A conventional induction heating cooker which operates a plurality of inverters at the same time is, for example, the induction heating cooker disclosed in Patent Document 1.
FIG. 7 is a diagram illustrating circuitry of the induction heating cooker described in Patent Document 1, and FIG. 8 is a chart of actuating signals of inverters in the induction heating cooker.
As illustrated in FIG. 7, the induction cooker described in Patent Document 1 includes: an AC power supply 101; first and second heating coils 102 and 103; a rectifier circuit 104 which rectifies the AC power supply 101; a smoothing capacitor 105 which smoothes a voltage of the rectifier circuit 104; first and second heating coils 102 and 103; first and second inverters 106 and 107 which convert outputs from the smoothing capacitor 105 into high-frequency powers and supplies the high-frequency powers to the first and second heating coils 102 and 103; an input current detection unit 108 which detects an input current from the AC power supply 101, and a control unit 109 which has a microcomputer for controlling operating states of semiconductor switches in the first and second inverters 106 and 107 to cause the detected value by the input current detection unit 108 to be a set value.
In the induction heating cooker 100 illustrated in FIG. 7, the control unit 109 controls the conduction times of the semiconductor switches in the first and second inverters 106 and 107 to cause the input current from the AC power supply 101 detected by the input current detection unit 108 to be a previously set current value. As a result, required high-frequency currents are supplied to the first and second heating coils 102 and 103 which are connected to the first and second inverters 106 and 107.
High-frequency magnetic fields are induced by the high-frequency currents in the first and second heating coils 102 and 103, and the high-frequency magnetic fields are applied to a load such as a pot which is magnetically coupled to the heating coil. The applied high-frequency magnetic fields induce an eddy current in the load such as a pot, and the pot is heated by the surface resistance of its own and the eddy current.
In the case where the first and second heating coils 102 and 103 heat the pot at the same time, the first inverter 106 has the conduction time of the semiconductor switch controlled to cause the input power to the first heating coil 102 to be P1 in an operation mode 1, as illustrated in FIG. 8. Further, the first inverter 106 has the conduction time of the semiconductor switch controlled to cause the input power to the first heating coil 102 to be P3 in an operation mode 2.
The second inverter 107 has the conduction time of the semiconductor switch controlled to cause the input power to the second heating coil 103 to be P2 in the operation mode 1. Further, the second inverter 107 has the conduction time of the semiconductor switch controlled to cause the input power to the second heating coil 103 to be P4 in the operation mode 2.
The operation mode 1 and the operation mode 2 are repeated to the first and second inverters 106 and 107 to cause the first and second heating coils 102 and 103 to alternately heat the pot with different input powers.
Patent Document 1: JP 2011-150797 A